length of 300 Weatherby actions vs 257

stevecrea

March 04, 2009 11:24

I have noted that the overall length of the 300 Weatherby is 3.562 inches, versus the .257 Weatherby at 3.250. The base diameter of the 300 is actually slightly smaller than the 257, at .512 versus .514, and the base diameter of the 300 is also slightly smaller at .531 versus .534.

My question is: Can the 300 or 340 Weatherby actions be readily converted to 257, 270, or 7mm Weatherby? Does anyone know if the 300 and 340 actions used by Weatherby are actually a bit longer than the 257, 270, and 7mm?

Thank you for your input.

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  nononsense

  March 04, 2009 11:57

  stevecrea,
  
  First of all, let me state that there are variations in the manufacturing of cartridge cases. The standard sizes should be referred to rather than these drawings that have been made from measuring one piece of brass. It keeps things simple.
  
  Standard Belted Magnum general dimensions:
  
  Rim = 0.532"
  
  Head just above belt = 0.512"
  
  Case length = 2.500" (there are exceptions)
  
  Overall loaded length 3.340"
  
  Long Belted Magnum general dimensions (H&H length)
  
  Rim = 0.532"
  
  Head just above belt = 0.512"
  
  Case length = 2.800" (there are exceptions)
  
  Overall loaded length = 3.600"
  
  Measure some brass that you have on hand and you'll find that the dimensions aren't even close any more, they are smaller.
  
  The Weatherby Mk V actions are long to begin with. The magazines are usually blocked at the rear in order to allow the use of shorter cartridges. This way, Weatherby makes one action and uses magazines to accommodate the range of cartridges.
  
  Yes, you could use the .300 WBY action for the .257 WBY by blocking the rear of the magazine and then adjusting the feeding. Sometimes it doesn't take much work to get these to feed but hold the rifle in a padded vise and practice feeding from the magazine while watching the process closely to make sure.
  
  Best.

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